update readme

implementation/16-caching/src/Middleware/CacheMiddleware.php

@@ -0,0 +1,36 @@
+<?php declare(strict_types=1);
+
+namespace Lubian\NoFramework\Middleware;
+
+use Laminas\Diactoros\Response;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Symfony\Contracts\Cache\CacheInterface;
+use Symfony\Contracts\Cache\ItemInterface;
+
+use function base64_encode;
+
+final class CacheMiddleware implements MiddlewareInterface
+{
+    public function __construct(private CacheInterface $cache, private Response\Serializer $serializer)
+    {
+    }
+
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        if ($request->getMethod() === 'GET') {
+            $key = (string) $request->getUri();
+            $key = base64_encode($key);
+            $callback = fn () => $handler->handle($request);
+            $cached = $this->cache->get($key, function (ItemInterface $item) use ($callback) {
+                $item->expiresAfter(120);
+                $response = $callback();
+                return $this->serializer::toString($response);
+            });
+            return $this->serializer::fromString($cached);
+        }
+        return $handler->handle($request);
+    }
+}